Pollution control devices are employed on motor vehicles to control atmospheric pollution. Such devices include catalytic converters and diesel particulate filters or traps. Catalytic converters typically contain a ceramic monolithic structure which supports the catalyst (i.e., a catalyst carrier or element). Diesel particulate filters or traps are typically wall flow filters which have honeycombed monolithic structures typically made from porous crystalline ceramic materials (i.e., filter element). Each of these devices has a metal housing (typically stainless steel) in which the pollution control element is contained. A mat comprising ceramic fiber is typically used to mount and protect the pollution control element within the housing. Filter elements, as well as catalyst carriers, can have walls with a catalyst thereon. The catalyst oxidizes carbon monoxide and hydrocarbons, and reduces the oxides of nitrogen in engine exhaust gases to control atmospheric pollution.
Mounting mats comprising ceramic fibers, which are used in such devices, are usually composed of up to 10% organic binder. The binder is used to hold the fibers together. Without such a high binder ratio, many problems can occur such as, for example, surface cracks in the mat during assembly of the pollution control device, low tensile strength of the mat and a lower bulk density.
The present invention is directed to providing a low binder content mat for use in a pollution control device, which does not exhibit one or more of such problems.